#include<list>
#include<iostream>
using namespace std;
int main()
{
	list<int> monkeys;
	int n,m;
	while(true){
		cin>>n>>m;
		if(n==0 && m==0)
		break;
		monkeys.clear();
		for(int i=1;i<=n;++i)
		monkeys.push_back(i);
		list<int>::iterator it = monkeys.begin();
		while(monkeys.size()>1){
			for(int i = 1; i < m; ++i){
				++it;
				if(it == monkeys.end())
				it == monkeys.begin();
			}
			it = monkeys.erase(it);
			
			if(it == monkeys.end())
			it = monkeys.begin();
		}
		cout<<monkeys.front()<<endl;
	}
	return 0;
}